Microbial contamination of water delivered by dental units has long been recognized as undesirable, and considerable effort has gone into studying the problem and its solutions. Currently available technology is capable of delivering sanitary water, but numerous studies have shown that most dental units are contaminated with large numbers of rnicroorganisms because of poor maintenance and cannot meet even potable water standards. Using a non-toxic redox dye and a fluorescent probe, Lynntech, Inc., proposes to construct a sensor capable of measuring bacterial concentrations in the range of 10 to 10/6 microorganisms per mL in a timely manner. The system will be completely automated, operate for pennies a day, measure only metabolically active bacteria, and can easily be integrated into existing systems. Providing daily feedback on water quality to dental personnel, the system will be capable of initiating corrective measure at a user-friendly time, eliminating down-time during normal office hours. Current technology for bacterial counts relies on slow, expensive, and labor-intensive methods that have not changed appreciably since the days of Pasteur. The proposed sensor will reduce the cost of these counts by a factor of 100 and allow these measurements to take place in the dental office by untrained personnel. PROPOSED COMMERCIAL APPLICATION: The development of biofilms in aqueous environments adversely affects the performance of industrial heat exchangers, water purification systems, food and beverage preparations, and medical systems. Development of a rapid, automated system that can be integrated into biocide control processes would be of enormous value in dealing with these multibillion dollar problems.